1. Technical Field
The present disclosure relates to misfire detection devices that detect misfires in spark ignition type engines. More particularly, the present disclosure relates to a misfire detection device capable of appropriately detecting a misfire even in a state in which combustion is unstable.
2. Related Art
For instance, a spark ignition type internal combustion engine such as an automotive four stroke gasoline engine is required to appropriately detect a misfire state in which an air-fuel mixture is not ignited normally from any cause and combustion is not carried out.
As a prior art related to a misfire detection device for an engine, for instance, Japanese Unexamined Patent Application Publication No. 2002-4936 describes that a detection threshold for detecting a misfire during rapid catalyst warm-up control is made different from that during usual operation so as to appropriately detect a misfire depending on an operating state of an internal combustion engine.
Japanese Unexamined Patent Application Publication No. H05-18311 describes that a detection value for misfire detection is changed so as to be hard to be determined as a misfire when an operating state of an engine is in a transient state such as warming-up-enrichment execution, rapid acceleration/deceleration, or warming-up retard.
Japanese Unexamined Patent Application Publication No. 2002-47996 describes that a detection value is calculated with use of a difference in a rotational speed from an adjacent cylinder and a difference between a rotational speed of a cycle and a rotational speed of a cycle immediately before the cycle of an identical cylinder, so as to reduce effects of manufacturing variation, attachment error and the like of a rotational angle sensor that detects a rotational angle of a crankshaft.
Japanese Patent No. 2853334 describes that learning correction is carried out by sequentially computing a correction coefficient of a crank angle sensor with respect to variation in vane angular intervals with use of a sum of cycles between crank angles of identification cylinder groups.
Japanese Unexamined Patent Application Publication No. H09-166042 describes that a transient correction term is used for computing a crank angle deviation time between cylinders in order to eliminate effects of transitional increase and decrease in rotation variation depending on an operating condition of an internal combustion engine at a time of rapid acceleration or rapid deceleration.
Japanese Unexamined Patent Application Publication No. 2006-152971 describes that a ratio of misfire detection values is computed between a cylinder having a possibility of misfire and cylinders before and after the cylinder at a time of detecting a misfire.